1. Field of the Invention
The present invention relates to a cigarette manufacturing machine and, more particularly, to an apparatus for supplying shredded tobacco to a conveyor belt used for conveying shredded tobacco onto a paper.
2. Description of Related Arts
A cigarette manufacturing machine consists mainly of a shredded tobacco supplying apparatus and a wrapping apparatus. The supplying apparatus comprises a belt conveyor for conveying shredded tobacco to the wrapping apparatus and a supply passage for introducing shredded tobacco with air flow to the belt conveyor. The belt (tobacco band) of the belt conveyor has a mesh structure having a plurality of tiny holes. This supplying apparatus applies an attracting force to shredded tobacco via the tiny holes to attract shredded tobacco to the belt surface.
The shredded tobacco coming out of the supply passage is attracted in layers to the running tobacco band and conveyed in the band running direction. The shredded tobacco reaching the terminal end of the belt conveyor is supplied onto a paper running in the wrapping apparatus and formed into a cigarette rod by being enveloped in the paper. Afterward, the cigarette rod is cut into individual cigarettes.
The cigarette manufacturing machine is required to produce large quantities of cigarettes. In order to increase the amount of shredded tobacco conveyed to the wrapping apparatus by the belt conveyor to meet this requirement, the amount of shredded tobacco supplied from the supply passage to the belt conveyor must be increased. If the supply amount of shredded tobacco is small, the amount per unit time of shredded tobacco conveyed from the supply passage to the wrapping apparatus via the belt conveyor decreases. As a result, the shredded tobacco put in a cigarette rod formed by the wrapping apparatus runs short, so that a good quality of cigarette rod cannot be achieved.
In order to increase the supply amount of shredded tobacco, firstly, the flow velocity of air and shredded tobacco in the supply passage is required to be increased, and secondly, the attracting property of shredded tobacco to the tobacco band is required to be enhanced.
For example, Unexamined Japanese Patent Publication No. 62-65673 discloses a cigarette manufacturing machine having a means for meeting the above second requirement. This known means of the cigarette manufacturing machine is provided with louvers (straightening vanes) arranged near the outlet of supply passage. The louvers serve to deflect the flow of shredded tobacco at the outlet of supply passage and to give the shredded tobacco a velocity component in the belt running direction while the shredded tobacco moves toward the tobacco band. If the velocity component in the belt running direction given to the shredded tobacco is approximately equal to the belt running speed, the attracting property of shredded tobacco to the belt (tobacco band) is enhanced.
If the belt running speed (the transfer speed of shredded tobacco conveyed by the conveyor) is increased and the flow velocity of shredded tobacco in the supply passage is increased extremely to further increase the production capacity of the cigarette manufacturing machine, the flow of shredded tobacco cannot be deflected suddenly even if louvers are arranged at the outlet of supply passage. That is to say, in the cigarette manufacturing machine having a supply passage extending from the side of belt conveyor toward the start end of belt conveyor, it is difficult in some case to give the shredded tobacco a velocity component in the belt running direction approximately equal to the belt running speed by means of the louvers arranged at the outlet of supply passage. In this case, when the shredded tobacco reaches the belt conveyor from the supply passage, part of the shredded tobacco collides with the tobacco band and is repelled. As a result, the amount of shredded tobacco attracted to the tobacco band, and in turn, the amount of shredded tobacco conveyed by the belt conveyor run short, so that the filling density of shredded tobacco in a cigarette rod decreases, by which the quality of cigarettes may be degraded.
Also, if the velocity component of shredded tobacco in the belt running direction differs greatly from the belt running speed, most shredded tobacco is attracted to the belt surface after rolling and moving on the belt surface. In this case, the position where the shredded tobacco is attracted to the tobacco band shifts from the initially intended position, so that the shredded tobacco is not attracted to the tobacco band in uniform layers. As a result, the filling density of shredded tobacco in a cigarette rod varies.